At 5/11/2007 09:45 AM, you wrote: > > There's good reason a "hot air" alarm probably went off for many > > of you when reading the article. > >I'm trying to figure out what his closing paragraph is trying to say: > >"A duplexer is working correctly when the sensitivity of the receiver is not >degraded when the transmitter becomes active. There are test procedures to >check this out, but the explanation of these tests is beyond the scope of >this article. [OK, I'll agree with him so far] However, should you hear a >slow oscillation of the transmitter when it turns on and off (a rate of >about 1-2 Hz rate on weak signals), then you do have duplexer >desensitization." > >What is this 1-2 Hz oscillation he's talking about?
In the context of the above, he's probably referring to the repeater transmitter cycling on & off due to loss of input signal when the TX is on due to desense. His hang time is probably only 1/2 second, hence the 1-2 Hz TX cycling period. BTW, I "quasi-simulcast" 2 UHF TXs about 70 miles apart; one is 1000 ft. AMSL & the other is 7000 ft. Some low hills between them but not much dirt otherwise. Only TX stabilization is temperature-controlled xtals on both. I try to keep them within 50 Hz but one xtal is aging a bit so right now they're about 200 Hz apart. Still, the heterodyne in the overlap areas is not bad & the system is perfectly usable everywhere. Only thing missing is the 2-channel voter. I have the hardware to put it together but there isn't enough usage of the system to justify the time spent to do it, so for now the 2 RXs are selected by CTCSS freq. Bob NO6B
